1. Field of the Invention
The invention relates to a method for load testing electrical systems of a motor vehicle, the operator control elements of the systems being activated on a test basis by at least one automatic activation device. In addition, the invention relates to a device for carrying out the aforesaid method.
2. Background Information
Electrical and electronic systems of growing complexity are being increasingly used in motor vehicles. For this reason, load testing such electrical systemsxe2x80x94which is also understood to refer to electronic systems in what followsxe2x80x94is particularly important. Load testing is intended to determine whether the systems have a sufficiently long service life and are sufficiently operationally capable. In such a context, specifically the operator control elements of the electrical systems are to be subject to testing because these are subjected to high mechanical loading, and are thus especially prone to wear and failure phenomena.
DE 31 05 491 C2 discloses in this respect a service-life testing device for electromechanical components of motor vehicles in which repeated activation of a switch can be performed in a test setup using stepping motors. At the same time, relevant data on the forces and moments occurring in the process can be recorded. Such a device permits a switch to be tested in terms of its behavior in the case of frequently repeated activation. However, it is apparent that the results acquired from such testing are not sufficient to evaluate the behavior of the switch under real conditions. For example, when electrical systems are used, including the operator control elements in a motor vehicle, under real conditions, numerous and complex interactions of the systems with one another and large degrees of variation of the loading occur owing to real ambient conditions.
Against this background, an advantage of the present invention is to make available a method and arrangement for load testing electrical systems of a motor vehicle which permit the behavior and the loading to be evaluated better under real conditions.
In accordance with the present invention, a method for load testing electrical systems (including electronic systems) of a motor vehicle is provided wherein the operator control elements of the systems are activated repeatedly for test purposes by means of at least one automatic activation device. The method is defined in that the electrical systems are tested in their installed, operationally capable state in a motor vehicle, and that the motor vehicle is subjected during this testing to a simulation of real ambient conditions.
The method according to the invention achieves a considerably better approximation to the real conditions of use of the electrical systems. This is done by virtue of the fact that the electrical systems or the associated operator control elements are not tested isolated in an artificial setup but rather are tested in their ultimate installation state in the motor vehicle. As a result, interactions between the electrical systems and also interactions between an electrical system or an operator control element and the motor vehicle are taken into account. For example, the behavior of a switch can differ greatly depending on the installation location and the method of installation, and the proposed method ensures that the testing is based on the actual installation conditions.
A further essential improvement in the test results is achieved by virtue of the fact that the motor vehicle is subjected during the testing to a simulation of real ambient conditions that can also have a considerable influence on the behavior of the systems and operator control elements.
In this context, the simulated ambient conditions can include in particular the ambient temperature. This is varied during the testing in a range that corresponds to the temperatures that can occur during real use of the motor vehicle. Typically, this temperature range lies between xe2x88x9240xc2x0 C. and +85xc2x0 C. The distribution of the testing time against the temperatures can be selected on the basis of the real temperature distribution to which a motor vehicle is typically subject during its service life. However, extreme temperatures are preferably used during the testing because they have a particularly loading effect and are thus highly significant in determining the loading limit.
Furthermore, the simulated ambient conditions can include the atmospheric humidity because this also has a considerable influence on the loading behavior of the systems or operator control elements to be tested. The atmospheric humidity is preferably varied during the test in the fluctuation range occurring under real conditions.
The simulated ambient conditions can also include the solar radiation that is preferably simulated by artificial irradiation with light with a suitable wavelength distribution (spectrum) and with a power of typically 4,000 W/m2.
Finally, the simulated ambient conditions can also include acceleration events of the motor vehicle that typically occur under real conditions. In particular, high-frequency acceleration events (e.g., impacts, vibrations, etc.) can understandably have a considerable influence on the mechanical behavior of the systems and operator control elements to be tested. In addition, acceleration events in the vertical direction are of special interest, and can be simulated by vertical movement of the contact faces of the wheels. Here, the contact faces under the wheels of the front axle should preferably be capable of being moved independently of the contact faces under the wheels of the rear axle. It is particularly preferred if all the contact faces of the wheels can be actuated and moved independently of one another. The acceleration program to which the motor vehicle is subjected can be predefined by acceleration events recorded during a real journey in order to ensure a particularly realistic simulation.
A robot is preferably used for automatically activating the operator control elements. Such a robot has the advantage that even complex operator control procedures and sequences of activations of various operator control elements can be performed with it in a flexible way, it being possible, for example, to predefine the movement sequences by means of so-called xe2x80x9cteach-inxe2x80x9d methods. Using a robot also has the advantage that it approximates particularly closely to the conditions when the operator control elements are activated by a driver, in terms of the application of force and the movement sequence.
During the activation of the control elements, the forces and torques occurring in the process are preferably sensed by sensor means on the activation device. The data acquired in this manner can then be evaluated later or simultaneously (online) with suitable analysis methods and provides valuable indications of behavior and changes of the operator control elements.
The activation of the operator control elements of the electrical systems is advantageously carried out in such a way that the forces and torques occurring in the process vary in terms of their magnitude and their direction. This also makes the load testing approximate better to reality because the activation of such operator control elements by a human is always subject to certain variations. In particular, activation operations that are less than optimum or incorrect can also be carried out in order to sense their influence.
The invention also relates to a device for load testing electrical systems (including electronic systems) of a motor vehicle, which has an automatic activation device for activating the operator control elements of the systems. The device is defined in that it contains a simulation chamber, in which a motor vehicle that contains the systems to be tested can be accommodated and in which ambient conditions can be simulated for the entire motor vehicle. Furthermore, the automatic activation device is configured in such a way that, during the operating state, it can be arranged, within a motor vehicle, with the systems to be tested.
The aforesaid device permits the abovementioned method to be carried out so that the advantages described above can be achieved. In particular, greater approximation of the load testing to reality can be achieved by testing the systems in the installed state in a motor vehicle and under (simulated) ambient conditions.
The simulation chamber can in particular have an air-conditioning system with which real climatic conditions in terms of temperature, atmospheric humidity and the like can be simulated.
In addition, the simulation chamber can have radiators for outputting electromagnetic radiation of a suitable spectrum in order to simulate the effect of solar radiation.
Furthermore, the simulation chamber preferably contains what is referred to as a road simulator for simulating acceleration events that act on a motor vehicle during a journey. The road simulator can be formed in particular from contact faces for the wheels of a motor vehicle that can be moved separately in the vertical direction using an actuation means.
The activation device also advantageously contains sensors with which the forces and torques that occur during the activation of operator control elements of the electrical systems can be sensed. The signals of these sensors can be recorded or evaluated in real time in order to be able to draw important conclusions about the behavior of the operator control elements.
The activation device is preferably a robot. Such a robot has the advantage that even complex operator control procedures and sequences of activations of different operator control elements can be performed with it in a flexible way, it being possible, for example, to predefine the movement sequences by means of a xe2x80x9cteach-inxe2x80x9d procedure. Using a robot also has the advantage that it approximates particularly well to the conditions when the operator control elements are activated by a driver, in terms of the application of force and the movement sequence.
The robot is advantageously provided with a protective sleeve whose interior can be air-conditioned. In this way it is possible to ensure that the robot operates reliably irrespective of the (simulated) ambient conditions prevailing around it.
Further advantages, objects and features of the invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying figures showing illustrative embodiments of the invention.